1. Field of the Invention
The present invention relates to a developer for photosensitive polyimide precursors, and to a method of using it for patterning.
2. Description of the Related Art
In recent semiconductor industries, organic substances with good heat resistance such as polyimide resins and the like are being used as interlayer insulating materials, because of their good characteristics, in place of conventional inorganic materials.
Circuit patterning for semiconductor integrated circuits and printed circuits requires many complicated steps of, for example, forming a resist film on the surface of a substrate, removing the unnecessary part of the film through selective exposure and etching at a predetermined site, and rinsing the surface of the thus-processed substrate. For this, therefore, it is desired to develop heat-resistant photosensitive materials for resists that can be directly used as insulating layers after having been patterned through exposure and development.
For those, for example, heat-resistant photosensitive materials comprising, as the base polymer, photosensitive polyimide, cyclic polybutadiene or the like have been proposed. Above all, photosensitive polyimides are specifically noticed for those materials, as their heat resistance is good and impurities are easy to remove from them.
However, the base polymer itself of conventional photosensitive polyimides is poorly soluble in organic solvents. Therefore, patterning a film of such a poorly-soluble, photosensitive polyimide material with a conventional developer for photosensitive polyimide precursors to give good patterns often takes a lot of time for development. In addition, if the development time for it is not adequately settled, some undesired residues will remain after the development.
With the recent tendency toward the reduction in processing time in the art, a one-mask process is being employed in which the polyimide pattern formed is directly used as a mask and the underlying passivation film is etched via the mask. In this case, the polyimide pattern formed is required to be a good mask with dimensional accuracy with little fluctuation.